A variety of mechanically based light modulators have been proposed to date with applications ranging from telecommunications to flat panel displays. In general, such devices can be classified into different categories based on the particular technique used to act on or modulate light. The particular technique used to act on light may include the phenomena of reflection, diffraction, interference, or obstruction. Regardless of the particular technique used to act on light, a light modulator is subject to the design constraint of maximizing its active area, while minimizing the space which must be devoted to an inactive area comprising structural and mechanical components. The active area of a light modulator is that area of the modulator that directly acts on light. Typical components that make up the active area of a light modulator include mirrors, diffraction gratings, liquid crystal cells, and reflective or absorbing charged particles. Examples of the structural and mechanical components that make up the inactive area include hinges, support posts, springs, etc.
The Digital Light Processor (DLP) or Digital Mirror Device, described in various patents including U.S. Pat. No. 5,061,049, exemplifies a class of devices that exploit reflection. In this case directed reflection, i.e. a light beam is either directed towards a viewer via intervening optics, or away. The DLP attempts to maximize its active area by hiding its structural components underneath a mirror that acts as the modulating surface.
Devices which rely on diffraction, such as the Grating Light Valve described in U.S. Pat. No. 6,088,102, maximize active area by shrinking the size of the inactive structural components and using imaging optics to focus light onto the active area.
In interference based devices, such as the interferometer modulator illustrated in U.S. Pat. No. 5,835,255, attempts are made to minimize the inactive area devoted to structural components. Because interference based devices are large area direct view displays there are no focusing optics through which the viewer sees the display. In this case, the active area is such a large fraction of the device that the structural components have minimal effect on the overall performance of the display.
Modulators that rely on obstruction, for example shutters, can be designed to maximize active area as exemplified by the modulator of U.S. Pat. No. 5,078,479. This modulator, like the aforementioned interferometer modulator, exploits the relatively large size of the direct view pixels to its advantage. However, other designs of modulators that have superior mechanical attributes, for example the modulator described and illustrated in U.S. Pat. No. 6,775,048, are not inherently capable of maximizing active area. The modulator of U.S. Pat. No. 6,775,048 incorporates imaging optics that magnifies the pixel active area and allow for its projection onto a viewing screen. However, the optics does not allow the pixel array to be observed from more than one viewing angle, without the viewing screen.